A common form of breast prosthesis is worn externally to avoid unnecessary surgery. A common example of a breast prosthesis is disclosed in Canadian application 2,105,348 by Schulz et al. The prosthesis is formed by a flexible skin which defines the exterior shape of the prosthesis and which encapsulates a flowable gel therein. By defining the shape of the prosthesis solely by a thin exterior skin, only a limited number of sizes are available so that the prosthesis is ill suited to many users. Furthermore the resulting structure is very heavy and causes many problems to the user due to the shifting mass during various activities performed by the user. The construction is also susceptible to damage by puncturing the outer skin such that the prosthesis cannot be repaired and is no longer of use. Other problems associated with a prosthesis of this type include a fixed nipple location as the nipple location on the prosthesis will not react to different garment types in the same manner as a natural breast. Further problems arise due to the flexible skin required to encapsulate the rear side of the prosthesis which is worn against the skin of the wearer as the skin is not well-suited to accommodate different preferences of different users for comfort.